1. Field of the Invention
The present invention relates to a frequency block allocation apparatus, a frequency block allocation method, and a relevant computer program based on a single carrier frequency division multiple access (SC-FDMA) method.
Priority is claimed on Japanese Patent Application No. 2009-205885, filed Sep. 7, 2009, the contents of which are incorporated herein by reference.
2. Description of the Related Art
For frequency block allocation, Patent Document 1 (Japanese Unexamined Patent Application, First Publication No. 2008-271321) discloses a technique in which an orthogonal frequency division multiple access (OFDMA) method is assumed. In the technique, for each frequency block, a terminal having a maximum allocation index is determined Among the determined terminals, one having the maximum allocation index is selected, and the frequency block assigned to the relevant maximum allocation index is allocated to the selected terminal.
However, in the above conventional frequency block allocation technique, the following problem occurs in the SC-FDMA method.
In the SC-FDMA method, sub-carriers arranged continuously or at regular intervals are allocated to communication terminals. Therefore, when allocating frequency blocks to each terminal, the continuous frequency blocks should be continuous. If a known frequency block allocation technique is used, a group of continuous frequency blocks, which include a frequency block having a maximum allocation index, are allocated, where the group of the continuous frequency blocks does not always produce a best channel quality.
For example, as shown in FIG. 12, if a frequency block “a” having a maximum allocation index is allocated to a terminal, a band A having continuous frequency blocks which include the frequency block “a” is allocated to the terminal. However, for the terminal, another band B has better channel quality than band A, where the band B does not include the frequency block “a” but has a frequency block “b” having a lower allocation index than the frequency block a. That is, in contrast to the OFDMA method, in the SC-FDMA method, a band including a frequency block having a maximum allocation index does not produce the best channel quality. Therefore, when applying the known frequency block allocation technique to the SC-FDMA method, the efficiency of the frequency usage may be degraded.